Many processes are known for the preparation of dialkylphenols, dialkylbenzenediols, naphthols and dialkylnaphthalenediols. Czech Patent CS 111,292 describes the alkylation of 2-methylhydroquinone, 2-tert-butylhydroquinone, and 2-tert-octylhydroquinone with diisobutylene in the presence of concentrated sulfuric acid and an inert solvent such as chloroform or a reactive solvent such as acetic acid or excess diisobutylene. The yields reported are of the order of 35%. See also, J. Pospisil and L. Taimr, Collect. Czech. Chem. Comm., 29 (1964), 381-5. British Published Patent Application GB 1,469,896 described a process for the synthesis of a hydroxy-(1,1,3,3-tetramethylbutyl)benzene by the reaction of a hydroxybenzene having one or more hydroxyl groups and optionally substituted, in particular hydroquinone, and a 2,2,4-trimethylpentene, i.e., one of its isomers: .alpha.-diisobutylene and .beta.-diisobutylene, or a mixture of the two, in the presence of highly concentrated sulfuric acid and ethylene glycol. According to this patent, highly concentrated sulfuric acid means a concentration in water that is greater than 90%, preferably in the range of 95.+-.3%.
Czech Patent CS 273,290 discloses the preparation of 2,3-bis-(1,1,3,3-tetramethylbutyl)hydroquinone by the alkylation of hydroquinone with diisobutylene using sulfuric acid as a catalyst in a mixture of methanol and aliphatic hydrocarbons. The yield reported is of the order of 65%. U.S. Pat. No. 3,373,210 describes a process wherein the alkylation is carried out in the presence of methanol and sulfuric acid as catalyst to achieve reported yields of 60%. Japanese Kokai 04-103,550 discloses the preparation of dialkylhydroquinones by treating hydroquinone with an olefin containing 6-30 carbon atoms using a strongly acidic polystyrene sulfonic acid-type cation resins wherein the resin preferably consists of particles having a particle diameter of not greater than 0.2 mm. 2,5-Bis(1,1,3,3-tetramethylbutyl)hydroquinone was prepared in a yield of 81% by the reaction of diisobutylene with hydroquinone at 125.degree. C. for 6 hours in the presence of &lt;0.05 mm diameter particles of a strongly acidic polystyrene sulfonic acid resin. Japanese Kokai 04-103,550 also discloses the preparation of 2,5-bis(1,1,3,3-tetramethylbutyl)hydroquinone in a 40% yield by the reaction of diisobutylene with hydroquinone at 35.degree. C. for 6 hours in the presence of acetic, phosphoric and sulfuric acids. Published PCT Patent Document WO 97/16402 discloses a process for the C-alkylation of a hydroxylated aromatic compound having at least one ortho or para hydrogen atom with respect to the hydroxyl group wherein the hydroxylated aromatic compound is contacted with a strong proton acid and a compound which forms a carbocation in the presence of the acid and in the presence of a solvent consisting of a water alcohol couple. In an example, 2,5-di-tert-octylhydroquinone is prepared by contacting hydroquinone with diisobutylene in the presence of water, methanol and benzenesulfonic acid over a period of 8.5 hours to obtain a reaction yield of 74% with an 88% conversion of the hydroquinone.